Plenty of people did in the past. For example, the Greek gods were powerful, but not all powerful. They had very human faults.

Is God Everywhere? GOD is fittingly described as omnipotent and omniscient—almighty and all-knowing. Yet, when attempting further to describe God’s greatness, some add a third term—omnipresent. They believe that God is present everywhere simultaneously. While none of these descriptive terms are found in the Bible, the first two are clearly supported by Scriptural teachings. (Genesis 17:1; Hebrews 4:13; Revelation 11:17) God is indeed omnipotent, and he is omniscient in the sense that nothing can be hidden from him. But is he omnipresent? Is God everywhere, or is he a person with a specific dwelling place? Where Is God? In several Bible verses, “the heavens” are mentioned as God’s “established place of dwelling.” (1 Kings 8:39, 43, 49; 2 Chronicles 6:33, 39) However, one Bible account describes the magnitude of Jehovah God with the following terms: “Will God truly dwell with mankind upon the earth? Look! Heaven, yes, the heaven of the heavens themselves, cannot contain you.”—2 Chronicles 6:18. “God is a Spirit,” says the Bible. (John 4:24) Therefore, he resides in a spiritual realm independent of the physical universe. When the Bible refers to “the heavens” as God’s dwelling place, it is referring to the loftiness of the place where he resides in contrast with the material environment in which we reside. In any event, the Bible teaches that God’s abode is, indeed, clearly distinguished from the physical universe but is at the same time a very specific location.—Job 2:1-2. God Is a Person Jesus spoke about Jehovah’s dwelling place when he said to his disciples: “In the house of my father there are many abodes. . . . I am going my way to prepare a place for you.” (John 14:2) Where did Jesus go? Eventually, he “entered . . . into heaven itself, now to appear before the person of God for us.” (Hebrews 9:24) This account teaches us two important facts about Jehovah God. First, he has a literal place of dwelling, and second, he is a person, not simply an indefinable force that resides everywhere. That is why Jesus taught his followers to pray this way: “Our Father in the heavens,” directing their prayers to a person, Jehovah, who is in a place, namely, the spiritual heavens. (Matthew 6:9; 12:50) This teaching was consistent with the way God’s people had been taught to pray for more than 1,500 years. The oldest writings inspired by God contain the following prayer: “Do look down from your holy dwelling, the heavens, and bless your people.”—Deuteronomy 26:15. God’s All-Reaching Holy Spirit While the Bible always refers to God as having a specific dwelling place, it often speaks of his holy spirit in ubiquitous terms. “Where can I go from your spirit, and where can I run away from your face?” asked the psalmist David. (Psalm 139:7) Some have been confused by such references and may conclude that God is omnipresent. Yet, when considering the context of this and other texts, it becomes clear that Jehovah’s holy spirit—or power in action—can be extended from his fixed location to any place in the material universe. Like a father’s hand extending down to console and support his children, Jehovah’s hand—or holy spirit—can extend to any part of the spiritual realm or the physical universe to accomplish Jehovah’s purpose. Hence, the psalmist could say: “Were I to take the wings of the dawn, that I might reside there in the most remote sea, there, also, your own hand would lead me and your right hand would lay hold of me.”—Psalm 139:9, 10. You Can Be God’s Friend Jehovah God humbly and lovingly allows himself and his dwelling place to be described in the human terms that most closely relate to his state of being. In this and other ways, it is as if he “stoops down to look on the heavens and the earth.” (Psalm 113:6, New International Version) Yet, God’s nature is truly beyond complete human comprehension. Jehovah is simply too magnificent, too great, and too wonderful to be fully described in human terms. So while the Scriptures speak about his heavenly abode as a place with a specific location, to understand such a spiritual dimension completely is simply impossible for humans.—Psalm 139:6. Still, there is great comfort in having some understanding of Jehovah’s true nature, realizing that he is not some indefinable, impersonal force permeating everything in the universe. Rather, he is an individual, with a specific place of dwelling and a definite personality characterized by love and tenderness. Such knowledge opens the door to the greatest opportunity possible for any human—the chance to have a lifelong, personal friendship with the Almighty Sovereign of the universe.—James 4:8.

I may have misunderstood your question. What do you mean by "powerful but not omnipotent"? I thought you asked "Why does virtually nobody believe in a God" (generally)? Because too many vile, opportunistic, scumbags throughout history have justified doing unscrupulous things in the name of the concept of God - the very God others claim is so loving and forgiving. The concept of God is generally used to codify or motivate by appealing to the basest part of an individual person's or collective population's ego. My take? I personally believe there is a God, but we all have God totally wrong and we may never have a proper perception of God until maybe after we die.

I guess you could say that I'm one of the few. I wholeheartedly believe in God, to the point where I don't consider it a belief but a knowledge of fact. Things that I've experienced have confirmed it to me. I do realize, however, that my own experiences are grossly insufficient for convincing others, so I typically keep them to myself. I consider God to be the master mathematician, chaotician, physicist, chemist, scientist, architect, engineer, and developer. I believe that He knows all of the laws and formulae that govern existence. After all, Jehovah means 'The Existing One.' I believe that He can mathematically predict all possible effects to all causes at any given point in spacetime, taking into consideration all known data to date, but that His observations are subject to the uncertainty principle. I also believe that He can apply the knowledge acquired in His calculations to cause any desired effect, no matter the scale or scope. I consider this to be wisdom and understanding, not omniscience or omnipotence, which are concepts manufactured to over-deify Him to the point that man's reverence turns to fear and disconnects him from his source.

My God is a loving God....is there room enough in your question for a loving God?

Because when you already the holy, righteous, sovereign, eternal, immutable, omnipresent, omnipotent, omniscient, truthful, merciful, and loving God, there really is no purpose for any other. "I am the LORD, that is My name; I will not give My glory to another, Nor My praise to graven images. -Isaiah 42:8 "You are My witnesses," declares the LORD, "And My servant whom I have chosen, So that you may know and believe Me And understand that I am He Before Me there was no God formed, And there will be none after Me. -Isaiah 43:10